The present invention relates to a kimchi fermentor, and particularly to a kimchi fermentor and control system thereof using kimchi curing sensor.
Kimchi is made of pickled vegetables including radish, cabbage and cucumber, and it is an indispensible dish in Korean cuisine. However, there have been numerous problems in its mass production and mass storage until now, because kimchi is a naturally fermented food and fermented kimchi has the defect of acidifying itself at room temperature.
Due to these problems, it is difficult to properly cure and produce kimchi on a commercial scale. While it is a fact that the problem of preserving properly cured kimchi for a long time has been encountered, it can not be said that kimchi is truly preserved as having its unique taste without controlling the fermentation for its curing. For example, with respect to the spread of refrigerator services for preserving kimchi, the frigerators have been used predominantly for preserving kimchi for long periods.
But kimchi stored in refrigerators is fermented even at relative low temperature. Also kimchi produces a unique odor which greatly influences other foodstuffs stored with it. Therefore, kimchi has not been produced to have the right taste in the refrigerator.
In light of this, it is an innovation if kimchi can be easily prepared to have the right taste, and the right taste can be preserved for a long time. Therefore, it is very ideal that kimchi has its degree of curing determined by means of a sensor, which can detect and measure the degree of curing of kimchi based on physiology and kimchi can be stored with the right taste for a long period.
But, the conventional method for automatically preparing kimchi includes only the steps of pickling kimchi and then controlling the fermentation period and temperature. Thus, the undesirable results have been caused as a result of either the kimchi manufacturing process or by the fermentation period and temperature, or the type of spice and the sauce quantity, etc.
That is to say, kimchi is a product with the sour taste of the organic acid obtained when the microorganism is increased in the pickled vegetable and the fermentation phenomenon occurs during the kimchi curing. It is well known that the taste of kimchi is greatly influenced by the type of the ,vegetable to be used, the type of the organism associated with kimchi, and the salt concentration and the temperature acting decisively to the increase of the number of microorganisms.
Thus, the design and construction of a kimchi fermentor must consider the fermentation physiology of kimchi. Also it has been the important task that in order to automatically manage the curing of kimchi, optimum control variables be derived to correspond to the degree of curing of kimchi. Then, the kimchi fermentation characteristics reported in Korea and overseas are its acidity or the pH. Thus the present invention aims at the design and construction of a kimchi fermentor, which uses the change in acidity pH as the measuring variables. But, if the acidity measuring equipment is installed in a home refrigerator, costs would be very expensive and uneconomical. Further, even if an acidity sensor is used in the refrigerator, the standard buffer solution must be used and thereby it can not remove the possibility that kimchi may be contaminated by the buffer solution. Also if the acidity electrode happens to be broken accidently, it can not prevent the risk that mercury and silver may cause serious contamination, because mercury and silver are the constituent parts of the electrodes. Therefore, it is very important that new variable capable of indicating kimchi curing should be founded.
Further, neverthless the variable adapted to the automatic control of kimchi fermentator has a problem in the measurement it must have a facility, which is easily converted into an electric signal having reliablity. Thus, it is further desirable for a kimchi fermentor to have a variable, which is economical and stable electric signal.
Thus, in order to find a variable adapted to kimchi curing, pressure changes relative to kimchi juice and the amount of gas produced during fermentation have been measured. That is, the representative physical change after preparing kimchi is to produce kimchi juice. Therefore it is known that changes in the amount of kimchi juice are easily measured and also are easily converted into electric signals, but it has been proven that the change of the amount of juice is caused by the protoplasm separation phenomenon and is in equilibrium sooner, whereas the amount of kimchi juice formed under various artificial temperatures and conditions have not for the most part been changed and influenced by the high or the low temperature. Thus it, has been known that the change in the amount of juice can not be used as a variable representing the beginning of kimchi curing or of the fermenting status.
Also, in connection with the amount of the gas generated while fermenting kimchi, it has been published that kimchi curing is closely related to the activities of microorganisms but is independent of acidity. Substantial kimchi fermentation mechanism makes the group of the un-aerobic or facultative microorganism, including Lactobacillus plantarum, which dissimilates the vegetables directly by or the microorganism increase in the basic dissoluable filtered solution to produce the organic acid and CO.sub.2. At that time the concentration of the organic acid is representing the acidity, which had been broadly used as the index of kimchi curing. Thus it is found that if a method for effectively measuring the amount of such CO.sub.2 produced is developed, it has the high possibility of the practical application as a index of kimchi curing as much as acidity value is usually used. Especially the gas measurement is more easily performed than the acidity measurement but also the cost for constructing a gas measuring appartus can be realized at low prices.
Accordingly, a pressure cell was used to measure the amount of the gas produced by fermenting kimchi, in which a kimchi sample is put in the pressure cell and then this pressure cell is again inserted into the case having kimchi to be fermented. Herein it is noted that the pressure cell has a capillary tube connected to the transducer which measures the pressure and converts the pressure into an electric signal. Therefore the pressure produced in the pressure cell was measured through the capillary tube at the transducer. As a result, it was experimentally confirmed that the pressure in the cell had been representing a curve similar to that of the microorganism increase, but after the lapse of 24's times the pressure in the cell had not been further changed During this experiment, kimchi had its acidic taste when the pressure in the cell was at the highest level. Its taste was equal to that of kimchi when the CO.sub.2 gas is produced at the largest quantity.
Therefore it has been proven that the pressure cell can be used as the sensor for sensing the kimchi curing, but, it must prove the reproducibilty of the measure in order to be useful as a sensor. As to it, it had been observed whether the amount of kimchi sampled from the prepared kimchi is fermented in the sensor cell and which prepared kimchi is put in a kimchi case along with the sensor cell. As a result, it has been found that since the fermentation of kimchi is not relative to true cultivation but to natural increasement, the growth aspects of the bacterium differ between kimchi in a case and kimchi samples in the kimchi sensor was developed in accordance with the lapse of the fermenting time even though the same samples were used at the time being intended to prepare kimchi. That is, because the growth environment of the bacterium in the pressure cell is different from the growth environment of the bacterium in the kimchi case, the possibility for inhibiting the growth of the bacterium by the influence of the pressure in the cell cannot be overlooked. Thus the pressure cell does not have the same reproducibility as the sensor for sensing kimchi curing.
In the procedures of these studies, it has been found that kimchi induces generative of gas during fermentation, the gas generated as the products of the basic disassimilating metabolism and the respiration of the microorganism is dissolved in part in the kimchi solution but is mostly discharged out of the kimchi solution forming an air bubble. Then it has been observed that the generation of the air bubble is usually not performed at the beginning of the fermentation having the relatively lower concentration of the bacterium but upon reaching the logarithmic growth phase, air bubbles are significantly increased in the size and number and become capable of being seen with the naked eye. The present invention requires appartus which can collect the gas with the kimchi case being opened in order to overcome the disadvantages causing the failure of the control system due to the air explosure of the kimchi case due to less than perfect sealing of the pressure cell.
Considering these points, it should be noted that the sensor for sensing kimchi curing may have variables according to the kimchi preparing, if the sensor has the reproducibility and senses the curing degree of kimchi under various temperatures and conditions. Thus if this kimchi curing sensor is developed, a kimchi fermentor is easily constructed. Also a kimchi fermentor must be easily controlled by its system on the basis of the varibles obtained from the kimchi curing sensor. Since the kimchi fermentor designed or configured on the basis of the fermenting process, the fermenting procedure must be accurately measured, and kimchi fermenting status and environment must be controlled before executing the design of the refrigerator. Also the design of the kimchi fermentor must not ignore the growth characteristics of the microorganism and includes physiological characteristics, the mechanical characteristics and the electronic characteristics that is the control system, considered as one system. For example, it takes about one week to complete the procedures including the steps of pickling kimchi and curing it through the fermentation. Further kimchi fermentation must be accompanied through reiterated experiments because it is not a true cultivation which has its properly configured method relative to the automatic fermenting system of kimchi. Therefore the fermenting control system kimchi must include all parts substantially required for the design of a kimchi fermentor as well as the measuring and controlling systems.